The phrase refers to an activity wherein individuals consume alcoholic beverages contingent upon specific occurrences within the 2008 satirical action comedy film, Tropic Thunder. For example, a pre-determined rule might mandate a drink each time a particular character uses a catchphrase, or whenever an explosion occurs on screen.
Such practices are often implemented to enhance the viewing experience of movies, introducing an interactive element. These activities can foster camaraderie amongst participants and add levity to the act of watching a film. The origins of such viewing enhancements are difficult to pinpoint, but they are a common pastime amongst groups of friends.